| 80 | − | 10 | x | + | 6 | x | − | 9 | = | 5 | x | − | 15 | − | 4 |
| Left side of the equation = | 71 | − | 4 | x |
| 71 | − | 4 | x | = | 5 | x | − | 15 | − | 4 |
| Right side of the equation = | 5 | x | − | 19 |
| 71 | − | 4 | x | = | 5 | x | − | 19 |
| - | 4 | x | − | 5 | x | = | - | 19 | − | 71 |
| - | 9 | x | = | - | 19 | − | 71 |
| - | 9 | x | = | - | 90 |
| 90 | = | 9 | x |
| 9 | x | = | 90 |
| x | = | 90 | ÷ | 9 |
| = | 90 | × | 1 9 |
| = | 10 | × | 1 |
| x | = | 10 |